This invention relates to a control for switching the current from an AC source to a load when multiple sensors determine that the load should be activated, with the sensors determining the range over which the load is activated.
Various electromechanical means have been utilized to provide control of power to a load during a portion of a sensors operating range. The load being activated when the sensor output is in a specified range. In these electromechanical devices the sensor range has been determined by mechanical means and usually covered a narrow operating range. An example of this type of electromechanical device is a thermostat where a set of contacts is closed when a preset temperature is reached; the contacts controlling power to a load. By mechanical hysteresis means the contacts remain closed until the sensor again passes through the preset temperature to a temperature point different from the preset temperature, at which time the contacts open and power is removed from the load. Controls of this type are necessary to prevent the rapid cycling of motors and other loads when controlled by sensor inputs.
Other types of control devices use electrical hysteresis to control a load over an operating range. These devices rely on the electrical hysteresis of the control to provide the operating range while the sensor provides one of the limit points of the range. The range of operation of this type control is relatively narrow.
With the foregoing in mind, it is a primary objective of the present invention to provide a new and improved limit controller that has a wide preset operating range.
Another object of the present invention is to provide a solid state controller that will energize a load with a DC or AC current over a preset operating range.
A further object of the invention is to provide a controller that has an operating range determined by at least two sensors. Still another object is to provide a controller that will activate a low or high impedance load over a predetermined operating range.